echolocationIn echolocation (also called sonar), a high-pitched sound (usually clicks) is sent out. The sound bounces off the object and some returns. The returning echo is interpreted to determine the object's shape, direction, distance, and texture. Dolphins (and other toothed whales) and some bats use sonar to navigate and find prey.

flipperFlippers are wide, flat limbs that many marine animals use for swimming. Seals and whales have flippers.

flukesThe tail of whales and dolphins is called the flukes (each half of the tail is called a fluke). Flukes have no bones in them. Whales swim by moving their flukes up and down in the water (fish move their tail left to right).

giant squidGiant Squid swim deep in the oceans. They have ten arms and their eyes are the size of basketballs.

gillsGills are organs that fish and amphibians use to breathe underwater.